Individuals with hearing restricted to the frequency region below about 500-750 Hz may benefit significantly from a combination of acoustic stimulation in the low-frequency region and electric stimulation in the higher frequency region. The advantage of electric-acoustic stimulation (EAS) is particularly apparent when listening to speech in the presence of competing speech, one of the most difficult listening situations for individuals with hearing loss. The often dramatic improvement in speech intelligibility when adding acoustic to electric stimulation occurs even though the acoustic stimulation alone often provides little or no intelligibility. The broad, long-term goal of the proposed research is to gain a better understanding of the acoustic cues and auditory processing underlying the benefits of EAS. In particular, the specific aims include identifying the acoustic cues in speech that are responsible for the benefits gained from low-frequency acoustic stimulation;determining the frequency extent and magnitude of low-frequency hearing that can support successful EAS;determining whether benefits similar to those seen with EAS can be observed in acoustic simulations of EAS by increasing the number of channels of stimulation in the low-frequency region;determining whether low-frequency acoustic stimulation helps the processing of interrupted speech;and determining whether low-frequency hearing in the implanted ear preserves important cues for understanding speech in the presence of spatially separated backgrounds. The research proposed here will include normal-hearing subjects listening to simulations of implant processing and cochlear implant patients with residual low-frequency hearing. This research should lead to a better understanding of EAS and could lead to improved speech reception for many current and potential patients and an increase in the number of individuals who might benefit from this relatively new and extremely promising technology. There are approximately 28 million individuals who suffer from hearing loss in the United States. A promising new approach to auditory rehabilitation for some of these includes a combination of acoustic stimulation and direct electrical stimulation of the auditory nerve. Additional research in this important new area is needed to broaden our theoretical understanding of electric-acoustic stimulation and to enhance its clinical efficacy.Recently, individuals fitted with cochlear implants have received a relatively short electrode array, intended to preserve their residual low-frequency hearing in the implanted ear. The addition of this low-frequency acoustic stimulation has been shown to dramatically improve speech reception both in real and simulated implant listening, particularly in background noise. The goal of this project is to gain a better understanding of the cues present in the low-frequency region that provide this benefit.